There’s a terrific moment midway through Rounders in which Mike McDermott (Matt Damon), a wizardly young cardsharp, describes what it’s like to play a hand of poker against your basic, everyday sucker — the kind of blind amateur you’d find clinging to the $5 tables in Atlantic City. The sucker, or fish, inevitably thinks that he’s got the game all figured out. ”If a fish acts strong,” explains Mike, ”he’s bluffing. If he acts meek, he’s got a hand.” Simple as that. What’s nifty — and funny — is the way that Mike lays out, and ridicules, a style of bargain-basement deception that’s probably about as far as most of us ever get in poker.

Mike has gotten a lot farther. He’s a great poker player, and not just because he can count cards or maintain a face as noncommittal as the Buddha’s. Mike watches the other players and, in effect, reads their minds. With each card dealt, he drinks in the reaction of his competitors — the microscopic glints of anxiety and satisfaction that let you know, if you’re a savvy enough student of human nature, just what’s going on in the hand of the person across the table.

Mike, a Manhattan law student, is a born hustler, or ”rounder,” who earns his tuition in high-stakes backroom card games. Poker, not law, is his passion, and the fun of the movie is the way it puts us right inside the psychological rush of the game. In Rounders, poker is a contest of will, deception, and daring, and the luck of the draw is virtually beside the point. It’s a duel of psych-outs, with the bluffs layered on top of other bluffs, then undercut by the biggest bluff of all: the hand that turns out to be exactly what the player implied it was (and therefore shouldn’t have been). For most of Rounders, we hardly see the hands being dealt, and that mirrors what’s going on in Mike, who barely needs to see those cards. He’s betting on the eyes of the players.

It may seem a bit much that Matt Damon is playing yet another genius, after Good Will Hunting, but Damon is a magical actor. His mind, as sharp and focused as a laser, beams out of the face of a vivacious choirboy, and, in nearly every scene, he invites you to share the jet-propelled pleasure of his precocious agility. No actor since Tom Cruise has made all-American cleanness so charismatic. During the card games, Damon speaks to us on the soundtrack, throwing insider poker lingo around like confetti and making the audience his coconspirators, and it’s one of the rare occasions of inspired voice-over. We’re hungry to know what’s in this kid’s mind.

Directed by John Dahl (The Last Seduction), from a script by David Levien and Brian Koppelman, Rounders doesn’t have much of a plot. Mike, after one too many hustles, loses his girlfriend, played by newcomer Gretchen Mol (who’s like a lacquered Renee Zellweger with an even littler-girl voice), and he hooks up with his old pal Worm (Edward Norton), a sleazy, scruffed-out hellion who has just gotten out of the slammer. Worm is in debt to a local mobster, and keeps getting into more debt; the only one who can save him is Mike, the straight shooter who’d never let a buddy down. If the story sounds familiar, it is — it’s yet another Mean Streets Lite. The ”bond” between Mike and Worm is, by now, a rather flimsy convention. Still, the two characters are convincingly in thrall to the excitement of gambling, and the film makes that addiction palpable. Norton, cast in what might have once been the Sean Penn role (hideous shirts, screw-you attitude), gives Worm a shifty, amphetamine soul and a pleasing alacrity — at the Taj Mahal in Atlantic City, Worm looks for a hooker just so that he can focus his concentration. Norton’s performance never really goes anywhere, but that’s okay, since the story is just an excuse to lead the characters from one poker table to the next.

Rounders, in the end, doesn’t have quite enough wild cards. There’s a good, tense scene in which Mike and Worm get caught hustling at a table of cops, but, for the most part, we know just where the story is headed: to the inevitable, bet-it-all, gambling-as-metaphor-for-life showdown. The film’s zestiest surprise is the succulent hambone theatrics of John Malkovich, who plays Teddy KGB, a slovenly Russian poker whiz, with an arrestingly cheesy malevolence and an accent as thick as Moscow fog. Funny? You bet, but anyone who laughs this performance off hasn’t registered how deeply the mischievous Malkovich is in on the joke. He’s Rounders’ ace in the hole. B